利用可见/近红外光谱技术对小米产地进行溯源研究

目的利用可见/近红外光谱技术对产自不同地区的晋谷21号小米进行溯源研究。方法使用近红外光谱仪获取产自洪洞、浮山、沁县3个不同地区的晋谷21号小米400~1004nm波段范围内的漫反射光谱;对光谱分别进行多元散射校正法(multiple scattering correction,MSC)、一阶导数法(first derivative,1St-D)预处理;对预处理光谱进行主成分分析,全交叉验证确定最佳主成分数量,获取主成分;同时选择预处理光谱特征波长。使用马氏距离法、线性判别法建立判别模型,最后用未知样品的验证准确率来表示模型的判别效果。结果原始光谱和MSC处理光谱提取特征波长分别建立的产地判别模型对3个不同产地的小米判别完全准确;1St-D处理光谱基于7个主成分结合马氏距离法和基于9个主成分结合线性判别法建立的2种判别模型对3个不同产地的小米亦实现完全准确判别。结论可见/近红外反射光谱技术用于小米产地的判别具有可行性,本研究可为小米产地的快速判别应用中提供技术基础。     

石墨烯量子点/CdS/CdSe共敏化太阳能电池

以三维锐钛矿TiO₂微球为上层光散射层材料, 以商业纳米TiO₂为下层连接材料, 采用刮刀法制备了一种新颖的双层TiO₂薄膜, 并应用于量子点敏化太阳能电池(QDSSC)。其中, 石墨烯量子点(GQDs)采用滴液法引入, CdS/CdSe量子点采用连续离子层吸附法(SILAR)制备。采用场发射扫描电镜、透射电镜、X射线衍射、紫外-可见漫反射光谱及荧光光谱对样品进行表征。实验还制备了CdS/CdSe量子点敏化及石墨烯量子点/CdS/CdSe共敏化太阳能电池, 并研究了石墨烯量子点及CdS不同敏化周期及对电池性能影响。研究结果表明, 石墨烯量子点及CdS不同敏化周期对薄膜的光学性质、电子传输及载流子复合均有较大影响。优选条件下, TiO₂/QGDs/CdS(4)/CdSe电池的光电转换效率为1.24%, 光电流密度为9.47 mA/cm², 显著高于TiO₂/CdS(4)/CdSe电池的这些参数(0.59%与6.22 mA/cm²)。这主要是由于TiO₂表层吸附石墨烯量子点后增强了电子的传输, 减少了载流子的复合。     

Synthesis of an anthraquinonoid disperse reactive dye based on a ligand-free Ullmann reaction

A new anthraquinonoid disperse reactive dye containing a dichlorotriazine reactive group was successfully synthesised on the basis of the Ullmann reaction in a ligand-free system by employing a copper(i ) iodide as catalyst, in combination with a subsequent condensation reaction. The parameters of the cross-coupling reaction between 1-chloroanthraquinone and 2,5-diaminotoluene sulphate were investigated and optimised, such as the molar ratio of the reactants, the dosage of potassium carbonate and copper(i ) iodide, the reaction temperature, and the reaction time. The results demonstrate that the dosage of potassium carbonate and the reaction time had significant impacts on the yield of the dye precursor, and an optimum synthesis process was also recommended. Moreover, the achieved dye was successfully characterised and confirmed from chemical structure and colour characteristics by employing Fourier transform infrared analysis, nuclear magnetic resonance spectroscopy, UV-vis absorption spectroscopy, elemental analysis, and liquid chromatography–mass spectrometry (LC-MS). Furthermore, a successful application of the obtained dye was achieved, with satisfactory coloration properties on silk and wool.     

恶意代码动态分析中的反虚拟化问题研究

反虚拟化是当前影响恶意代码动态分析系统全面获取样本行为数据的重要因素.本文提出从恶意代码动态分析环境的主机环境,网络环境和用户交互环境进行系统的反虚拟化对抗方法,并将反虚拟化对抗实现在已有的动态分析系统上,实验结果表明反虚拟化对抗有效的增强了动态分析系统获取样本行为数据的能力.     

An Efficient Framework for Multiple Subgraph Pattern Matching Models

With the popularity of storing large data graph in cloud, the emergence of subgraph pattern matching on a remote cloud has been inspired. Typically, subgraph pattern matching is defined in terms of subgraph isomorphism, which is an NP-complete problem and sometimes too strict to find useful matches in certain applications. And how to protect the privacy of data graphs in subgraph pattern matching without undermining matching results is an important concern. Thus, we propose a novel framework to achieve the privacy-preserving subgraph pattern matching in cloud. In order to protect the structural privacy in data graphs, we firstly develop a k-automorphism model based method. Additionally, we use a cost-model based label generalization method to protect label privacy in both data graphs and pattern graphs. During the generation of the k-automorphic graph, a large number of noise edges or vertices might be introduced to the original data graph. Thus, we use the outsourced graph, which is only a subset of a k-automorphic graph, to answer the subgraph pattern matching. The efficiency of the pattern matching process can be greatly improved in this way. Extensive experiments on real-world datasets demonstrate the high efficiency of our framework.

     

食品风味协同作用研究进展

随着消费者对食品风味质量的日益重视,食品风味逐渐成为研究热点。食品的香气馥郁复杂,难以准确定性定量,各种香气成分之间及其与食品基质间的相互作用导致混合香气的协同、加成、折中、掩盖等作用,这些作用决定了最终食品的风味和品质。目前,关于风味物质协同作用的研究主要集中香精调配中,鲜有文章系统地对食品中的风味物质协同作用进行阐述。本文主要综述了香气协同探究历程、宏观[阈值法、S型曲线法、风味活性值法(odor activity value,OAV)和σ-τ图法]研究方法和微观研究方法(离子浓度变化对嗅觉受体活性水平)的研究进展;总结了乳制品、酒类和肉类中发生的风味协同作用的规律和作用机制,并对未来的发展趋势进行了展望,以期能为食品风味和品质的改良提供理论依据。     

Uneven Evolution of Microstructure,Magnetic Properties and Coercivity Mechanism of Mo-Substituted Nd-Ce-Fe-B Alloys

The purpose of this paper is to study the influence of Mo addition on the phase morphologies,microstructures and magnetic properties of the designated alloys.It is found out that the coercivity Hcj increases unevenly from 12.2 kOe for (Nd0.8Ce0.2)13Fe82B5 to the maximum value of 13.3 kOe for (Nd0.8Ce0.2)13Fe80B5Mo2.The transmission electron microscopy images demonstrate that the grain size decreases with the addition of Mo,which indicates that Mo has grain refinement effect.The correlative analysis gives rise to the conclusion that the coercivity mechanism of the investigated alloys is dominated by pinning type.All in all,the enhancement of the magnetic properties is mainly attributed to the synergistic impact of grain refinement,pinning effects and the microstructural homogenization.The research may shed light on the potential development and application of rare earth-based counterpart magnets.     

Unsupervised and reliable image matting based on modified spectral matting

Spectral matting is the state-of-the-art image matting and also a milestone in theoretic matting research. For spectral matting without user intervention, the accuracy of alpha matte is low and the computational cost is high. Therefore, this paper presents a modified version of spectral matting to greatly increase the accuracy of alpha matte and effectively reduce the computational cost. In the proposed modified spectral matting, palette-based component classification is used to obtain reliable foreground and background components. Next, the corresponding matting components are obtained via a linear transformation of the smallest eigenvectors of the matting Laplacian matrix. Finally, the matting components of the foreground and the unknown regions are combined to from the complete alpha matte based on minimizing the matte cost. Moreover, image composition with consistency of color temperature is used to obtain the realistic image composition. Experimental results show that the proposed method outperforms the state-of-the-art methods based on spectral matting.     

样品前处理-离子色谱法应用于食品分析的 研究进展

离子色谱是无机和有机离子分析中的重要手段, 已经广泛应用于食品分析领域。但是样品的前处理往往占去大部分的分析时间, 而且是决定分析结果成败的关键因素。探索快速、高效、简便、自动化的样品前处理新方法已成为目前离子色谱研究中的前沿课题。本文综述了离子色谱样品前处理技术应用于食品分析的研究进展。通过分析样品的提取、净化、浓缩与富集痕量物质3个方面, 总结了样品前处理-离子色谱法在食品分析中的应用现状。其中, 样品的提取主要阐述了加速溶剂萃取和微波辅助萃取的研究; 样品的净化主要包括在线超滤法、在线渗析法等膜技术和采用了反相材料、离子交换树脂、螯合树脂和其他新型材料的固相萃取技术; 浓缩方法主要综述了微波浓缩和柱切换法的进展。     

一种动态OD矩阵估计算法的研究及应用

OD矩阵是智能交通的重要研究领域之一,是微观交通仿真、城市交通规划、管理和控制等的关键数据.本文将微观交通仿真与交通信号机监控系统相结合,提出一种基于极大熵法的动态OD估计算法.分析路段交通流的动态变化.为提高OD估计的精度,给出一种历史OD矩阵的递推方法.仿真结果表明本文方法是有效、可行的.